The use of focused ion-beam (FIB) microscopes has become common for the preparation of specimens for later analysis in the transmission electron microscope (TEM). The structural artifacts, and even some structural layers, in the device region and interconnect stack of current integrated-circuit devices can be too small to be reliably detected with the secondary electron imaging in a Scanning Electron Microscope (SEM), or FIB, which offers a bulk surface imaging resolution of approximately 3 nm. In comparison, TEM inspection offers much finer image resolution (<0.1 nm), but requires electron-transparent (<100 nm thick) sections of the sample mounted on 3 mm diameter grid disks.
The in-situ lift-out technique is a series of FIB milling and sample-translation steps used to produce a site-specific specimen for later observation in a TEM or other analytical instrument. Details on methods of in-situ lift-out may be found in the specifications of U.S. Pat. Nos. 6,420,722 and 6,570,170. These patent specifications are incorporated into this application by reference, but are not admitted to be prior art with respect to the present application by their mention in the background.
The process of in-situ lift-out can be simplified into three successive steps. The first is the excision of the lift-out sample using focused ion-beam milling and extraction of the lift-out sample from its trench. The second is the holder-attach step, during which the lift-out sample is translated on the probe tip point to the TEM sample holder. Then it is attached to the TEM holder (typically with ion beam-induced metal deposition) and later detached from the probe tip point. The third and final step is the thinning of the lift-out sample into an electron-transparent thin section using focused ion beam milling.
However, for in-situ lift-out to be practical for large-wafer FIB chambers or for high-volume TEM sample preparation, the nano-manipulator probe tips must be replaceable without the need to vent the vacuum chamber. Venting of the FIB vacuum chamber is time consuming. It disables the FIB during the venting and re-pumping cycle, and can eventually degrade the performance of the FIB if repeated often. Removing and replacing the entire nano-manipulator probe shaft or nano-manipulator mechanism by way of a vacuum airlock on the FIB chamber is not preferred, because the use of the airlock mechanism adds the extra risk of accidental chamber venting, and because this would require direct access by the user to the periphery of the FIB vacuum chamber. This practice is strongly discouraged by manufacturers of large-wafer in-line FIB's.
There is a need for a method and apparatus for handling one or more sample-tip assemblies without the need for venting the vacuum chamber to exchange probe tips. The proposed methods and apparatus disclosed here offer the benefits of dramatically reduced cycle time for in-situ lift-out and improved usage of in-line (within the process control flow) and off-line (external to the process control flow) analytical tools.